Low observable aircraft, missiles, ships and other vehicles are carefully constructed to minimize radar reflection. Large surface areas of such vehicles can be successfully treated, yet a small error, such as poor panel fit or an improper repair to a radar-absorbing coating thereon, can result in a radar cross-section of disproportionate magnitude with respect to the physical size of the defect or error. Typical problem areas are mismatched panel joints, discontinuities in radar-absorbing coatings, and other hidden damage that almost inevitably occur in an operational environment. Tests for such defects can be performed at manufacturing sites or radar ranges, but such require a large array of expensive radar test equipment and computers. Such tests are very difficult to perform an operational environment.
There also is a need to provide better, economical and safer means for nondestructive field testing of more conventional conductive structures in critical areas of flight vehicles. Available test systems, such as those that use x-rays are dangerous and difficult to use, whereas acoustic and eddy current test systems produce outputs, which are difficult to interpret or from which faults are difficult to precisely locate.
Therefore, there has been a need to provide a nondestructive testing device and method for both radar cross-section faults and physical defects, which is simple and easy to use, relatively inexpensive, robust, and whose results are easily interpreted.